Apparatus for inhibiting fuels from flowing out of fuel tanks

ABSTRACT

A device includes a housing fixed to an upper wall of a fuel tank, and having a communication opening in communication with a canister, a float valve received within the housing and floating on a fuel, and the float valve moving upward and downward so as to close and open the communication opening, and a tubular member communicating with the housing, and extending downwardly from the housing into the interior of the fuel tank. The device has through holes of a small diameter which are disposed near an upper wall of the fuel tank, and when the liquid level of the fuel in the fuel tank reaches the lower end opening of the tubular member, a pressure within the fuel tank increases, whereby the filling-up of the fuel tank is detected. When the liquid level of the fuel abnormally rises, the float valve closes the communication opening.

[0001] The present application is based on Japanese Patent ApplicationNo. 2001-364172, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] This invention relates to improved structure of a cutoff valveand full-tank detection means provided in a tank, which is suitablyadapted to fuel tank of an automobile.

[0003] A vaporized-fuel circulation system, called an evaporationcircuit, is provided in the vicinity of a fuel tank of an automobile.Vaporized fuel is fed from the fuel tank to an external canister by thisevaporation circuit, and is adsorbed by activated carbon or the like tobe temporarily stored therein, thereby preventing the increase of aninternal pressure of the fuel tank due to the increase of the vaporpressure. The canister is connected to an engine, and the vaporized fuelis expelled from the activated carbon by a negative intake pressure ofthe engine, and is mixed with a fuel-air mixture, and the adsorbedvaporized fuel is thus again used as the fuel.

[0004] In this evaporation circuit, naturally, an opening, called anevaporation opening, is formed in the fuel tank. Generally, thisevaporation opening is formed in an uppermost portion of the fuel tankin order to prevent liquid fuel from flowing into the evaporationcircuit. However, there is a fear that the liquid fuel flows into theevaporation opening when the liquid level of the fuel moves up and down.If the liquid fuel flowed as far as the canister, this liquid fuel wouldbe adsorbed by the activated carbon, so that the adsorption of thevaporized fuel by the activated carbon would be adversely affected.

[0005] Therefore, a cutoff valve has heretofore been provided at theevaporation opening. In many cases, a float valve is used as the cutoffvalve as described later. When the liquid level of the fuel rises beyonda predetermined normal level, the float valve floats up because of itsbuoyancy to close the evaporation opening, thereby preventing the liquidfuel from flowing into the evaporation circuit.

[0006] Full-tank detection means for detecting the filling-up of thefuel tank at the time of refueling is provided at the fuel tank. In manycases, this full-tank detection means comprises a float valve asdescribed later, and this float valve closes an opening in the fuel tankso as to increase the internal pressure of the fuel tank, therebyautomatically stopping the operation of a refueling gun.

[0007] For example, JP-A-11-229984 discloses a device which comprises ashut-off valve for flowing gas, containing fuel vapor produced in alarge amount at the time of refueling, to a canister, and a cutoff valvefor flowing the gas, containing the fuel vapor, to the canister duringthe time when the refueling is not effected.

[0008] This device is provided at an upper wall of the fuel tank, andcomprises an upper housing 100 and a lower housing 200 as shown in FIG.8. The upper housing 100 is in communication with the canister (notshown). The upper housing 100 and the lower housing 200 communicate witheach other via a first communication passage 101 of a smaller diameterand a second communication passage 102 of a larger diameter.

[0009] A first float 201 and a second float 202 are provided in thelower housing 200, and the first float 201 is provided in a first space201 a of a tubular shape, and the second float 202 is provided in asecond space 202 a of an annular shape formed around the first space 201a in isolated relation thereto. The second float 202 is formed into atubular shape.

[0010] The first float 201 has a valve member 201 b formed at its upperend, and the second float 202 has a valve member 202 b formed at itsupper end, and when the liquid level of the fuel moves up and down, thevalve member 201 b closes and opens the first communication passage 101,and also the valve member 202 b closes and opens the secondcommunication passage 102. The first float 201 and the second float 202are urged upward by springs 203 and 204, respectively, but before thefirst float 201 or the second float 202 is floated up by the liquidfuel, the valve member 201 b or the valve member 202 b opens the firstcommunication passage 101 or the second communication passage 102.

[0011] A small hole 205 is formed in an upper portion of the lowerhousing 200, and the first space 201 a communicates with a gas phaseportion of the fuel tank via the small hole 205. Further, communicationholes 206 are formed in bottom portions of the first and second spaces201 a and 202 a, respectively, and each of the first and second spaces201 a and 202 a communicates with the interior of the fuel tank via thecorresponding communication hole 206. The lower housing 200 includes acentral tubular portion 207, which extends downwardly from the firstspace 201 a, and is open to a lower end of this lower housing, and anannular tubular portion 208 which extends downwardly from the secondspace 202 a in surrounding relation to the central tubular portion 207,and is open to the lower end of this lower housing.

[0012] In this device, in the case where the liquid level of the fuel isdisposed at a position 300 lower than the lower end of the lower housing200, the vaporized fuel enters the first space 201 a and the secondspace 202 a via the respective communication holes 206, and flowsthrough the first and second communication passages 101 and 102 into thecanister via the upper housing 100. Also, there is another flow ofvaporized fuel which enters the first space 201 a via the small hole205, and flows into the canister via the first communication passage 101and the upper housing 100. As a result, the internal pressure of thefuel tank will not increase, and therefore the refueling operationproceeds smoothly.

[0013] Then, after the liquid level of the fuel reaches a position 301of the lower end of the lower housing 200, the pressure within thecentral tubular portion 207 becomes higher than the pressure within thefuel tank, and therefore the liquid level of the fuel rises only withinthe annular tubular portion 208, and the fuel enters the second space202 a through the communication hole 206 to float the second float 202.When the second float 202 thus floats, so that the valve member 202 bcloses the second communication passage 102, the pressure within thefuel tank abruptly increases, so that an automatic stop function of arefueling gun is exercised, thereby stopping the refueling. Therefore,the filling-up of the fuel tank can be detected.

[0014] When the liquid surface of the fuel is disturbed to rise, forexample, during the travel of the car, the second float 202 first floatsup to close the second communication passage 102, thereby preventing theliquid fuel from flowing into the upper housing 100. When the liquidsurface is more vigorously disturbed to rise, the first float 201 alsofloats up to close the first communication passage 101, therebypreventing the liquid fuel from flowing into the upper housing 100.

[0015] In the above device, there are provided the two float valves andthe two communication passages, and therefore there is encountered aproblem that it is difficult to design the device in such a manner thateach of the two float valves can operate accurately. There is anotherdisadvantage that the cost is high since the number of the componentparts is rather large. And, the second float 202 and the second space202 a are large in diameter, and this invites a problem that themounting space is much limited.

[0016] Furthermore, in the case where this device is used in fuel tanksof different shapes and capacities, it is necessary to produce manykinds of lower housings 200 and second floats 202, having differentshapes, and this invites a problem that much time and labor arerequired.

SUMMARY OF THE INVENTION

[0017] This invention has been made under the above circumstances, andan object of the invention is to provide a structure which enables acutoff operation and a full-tank detection with a simpler construction,and can be easily applied to many kinds of fuel tanks.

[0018] The above problems have been solved by a fuel outflow-limitingdevice of a fuel tank of the invention characterized in that the devicecomprises a housing, which is fixed to an upper wall of the fuel tank,and has a communication opening in communication with a canister; onefloat valve which is received within the housing, and floats on a liquidfuel, and moves upward and downward in accordance with the upward anddownward movement of a liquid level of the fuel so as to close and openthe communication opening; and one tubular member which communicateswith the housing, and extends downwardly from the housing into theinterior of the fuel tank, and is open at its lower end;

[0019] the housing has a through hole of a small diameter which isdisposed near to an inner surface of an upper wall of the fuel tank, andcommunicates the inside and outside of the housing with each other, andwhen the liquid level of the fuel in the fuel tank reaches the lower endopening of the tubular member, a pressure within the fuel tankincreases, so that the tubular member detects the filling-up of the fueltank, and when the liquid level of the fuel rises beyond a predeterminednormal level, the float valve closes the communication opening.

[0020] Preferably, the tubular member is separate from the housing, andis hermetically fixed to the housing. Preferably, an upwardly-opentubular portion is formed within the housing, and is disposed around anouter periphery of the float valve.

[0021] Another aspect of the invention provides an outflow-limitingdevice of a tank, comprising:

[0022] a housing forming a float valve chamber therein and provided witha communication opening to an outside of the fuel tank;

[0023] tubular member communication and extending downward from thehousing in a direction of liquid level of a fuel and having a lower endopening at a lower end thereof;

[0024] a through hole having a smaller diameter than the lower endopening, formed on a position upper than the lower end opening so as tocommunicate with the tubular member or the float valve chamber;

[0025] a float valve provided in the float valve chamber and having avalve member for closing the communication opening;

[0026] wherein the tubular member is pronged into the fuel when theliquid level of the fuel reaches a first liquid level of the fuel sothat communication of the tubular member to a gas phase located on anupper portion on the inside of the fuel tank is cut, whereby evacuationof vaporized fuel decreases.

[0027] In a fuel outflow-limiting device of the present invention, in anormal condition in which a liquid level of fuel is disposed below atubular member, a float valve is supported within a housing because ofits own weight, and opens a communication opening leading to a canister,as in the conventional structure. Therefore, gas within the fuel tankpasses through the tubular member and the housing, and flows into acanister via the communication opening, thereby adjusting the pressurewithin the fuel tank.

[0028] When the liquid level of the fuel within the fuel tank rises toreach a lower end opening of the tubular member at the time ofrefueling, gas within the fuel tank enters the housing only via throughholes of a small diameter formed in the housing, and at this time thethrough holes offer a high resistance to the passage of the gas.Therefore, when the liquid level of the fuel rises to reach the lowerend opening of the tubular member, the pressure within the fuel tankincreases, thereby automatically stopping the operation of a refuelinggun. Namely, the filling-up of the fuel tank can be detected by thetubular member, and the liquid level of the fuel, representing thefull-tank position, can be adjusted by adjusting the length of thetubular member. Incidentally, the filling-up of the fuel tank in thisapplication means a state that the level of the fuel in the tank reachesat a level in which the refuel gun is automatically stopped.

[0029] When the liquid level of the fuel abnormally rises beyond thepredetermined level because of acceleration and so on during the travelof the vehicle, so that the float valve floats, the float valve ispressed against the communication opening portion because of itsbuoyancy to close this communication opening. As a result, the liquidfuel is prevented from flowing into the canister via the communicationopening, and the float valve functions as a cutoff valve.

[0030] The housing may be integral with the fuel tank or may be separatefrom the fuel tank. The housing may be provided in a gas phase portionof the fuel tank or may be arranged to extend through an upper wall ofthe fuel tank. A method of fixing the housing and the fuel tank togetheris not particularly limited to welding, fastening by bolts and theintegral molding of the two members. Although generally, thecommunication opening, communicating with the canister, is provided atthe uppermost portion of the housing, this communication opening is notparticularly limited to any specified position in so far as the floatvalve can close the communication opening by its buoyancy. Thecommunication opening, leading to the canister, may have any suitableshape in so far as the float valve can close it.

[0031] The through holes of a small diameter, formed in the housing,communicate the interior of the fuel tank with the interior of thehousing, and the number and diameter of the through holes are important.If the diameter of the through holes is too large or the number of thethrough holes is too large, it is difficult to increase the internalpressure of the fuel tank when the fuel tank becomes full, and thereforeit is difficult to automatically stop the operation of the refuelinggun. If the diameter of the through holes is too small or the number ofthe through holes is too small, it is difficult to flow the gas withinthe fuel tank into the canister, so that the cutoff valve fails toproperly adjust the internal pressure. Therefore, the diameter andnumber of the through holes need to be accurately determined in atrial-and-error manner in accordance with the capacity of the fuel tankand so on. In order to prevent the liquid fuel from entering thehousing, it is preferred to provide the through holes as close to theupper surface of the fuel tank as possible.

[0032] The float valve can be similar in material and shape toconventional float valves. The float valve may be so constructed that itcan float only by the difference between its apparent specific gravityand the specific gravity of the fuel, or the float valve may use aurging force of a spring or the like so as to assist its buoyancy.

[0033] Further the sealing member may include a seal aperture connectedto the communication opening and having a smaller diameter than thecommunication opening and a seal projection configured to be openableand closable of the seal aperture.

[0034] Preferably, the float-valve has a double-seal structure in whichan inner seal member is held in the float valve so as to move upward anddownward as disclosed, for example, in JP-A-2-112658. In such astructure, there is eliminated a disadvantage that the float valve failsto move downward even when the liquid level descends after the floatvalve is brought into intimate contact with the communication openingportion leading to the canister. Therefore, the dynamic sealing abilityis enhanced when the liquid surface of the fuel is vigorously disturbedto rise, and therefore the function of the cutoff valve is moreeffectively performed.

[0035] Preferably, an upwardly-open tubular portion is formed within thehousing, and is disposed around the outer periphery of the float valve.By forming this tubular portion, the liquid fuel, passing through thethrough holes of a small diameter in the housing, impinge on the tubularportion, and the flow of the liquid fuel is regulated, so that theliquid fuel is prevented from intruding into the communication openingleading to the canister, and the inflow of the liquid fuel can beprevented more positively. Preferably, the level of this tubular portionis higher than the upper surface of the float valve located in its lowerposition in the normal condition.

[0036] The length of the tubular member is so determined that the lowerend opening thereof is disposed at the liquid level of the fuel when thefuel tank is full of the fuel. Therefore, the length of the tubularmember varies depending on the capacity and shape of the fuel tank, butin the present invention the full-tank detection can be effected merelyby adjusting the length of the tubular member. Therefore, if the tubularmember is formed into the maximum length, the full-tank liquid levelposition can be defined merely by cutting the tubular member into adesired length in accordance with the car kind or the like, andtherefore it is not necessary to produce various fuel outflow-limitingdevices for different fuel tanks, and the time and labor can be greatlyreduced. The tubular member can be separate from the housing, and aplurality of kinds of tubular members of desired lengths can beprepared.

[0037] The tubular member may be fixed to the lower portion of thehousing, or the upper end portion serves also as a peripheral wall ofthe housing. Preferably, at least the lower end opening of this tubularmember is smaller in diameter than the housing. With this construction,even when the liquid level of the fuel is disturbed to rise during therefueling operation, the full-tank detection can be effected accurately.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038]FIG. 1 is a front-elevational view of one preferred embodiment ofa fuel outflow-limiting device of the present invention;

[0039]FIG. 2 is a cross-sectional view thereof of the fueloutflow-limiting device of the above embodiment;

[0040]FIG. 3 is a cross-sectional view of a second embodiment of a fueloutflow-limiting device of the invention;

[0041]FIG. 4 is a cross-sectional view, showing another method of fixingthe fuel outflow-limiting device of the second embodiment to a fueltank;

[0042]FIG. 5 is a cross-sectional view, showing a further method offixing the fuel outflow-limiting device of the second embodiment to thefuel tank; and

[0043]FIG. 6 is a cross-sectional view, showing a further method offixing the fuel outflow-limiting device of the third embodiment to thefuel tank; and

[0044]FIG. 7 is a cross-sectional view, showing a further method offixing the fuel outflow-limiting device of the fourth embodiment to thefuel tank; and

[0045]FIG. 8 is a cross-sectional view of a conventional fueloutflow-limiting device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] The present invention will now be specifically described by wayof preferred embodiments.

[0047] (First Embodiment)

[0048]FIG. 1 is a front-elevational view of one preferred embodiment ofa fuel outflow-limiting device of the present invention, FIG. 2 is across-sectional view thereof. This fuel outflow-limiting device mainlycomprises a lid member 2, which is fixed by welding to an upper surfaceof an automotive gasoline tank 1 (made of a resin), and is disposedabove an opening 10 formed in an upper wall of the gasoline tank 1, atubular member 3 fixed by welding to a lower surface of the lid member2, a housing 4 formed at an upper portion of the tubular member 3, and afloat valve 5 mounted in the housing 4 so as to move upward and downwardin a direction of the liquid level.

[0049] The lid member 2 is injection molded of a polyethylene resin anda polyamide resin, and includes a nipple 20 extending parallel to theupper surface of the gasoline tank 1, and a tube, communicating with acanister, is adapted to be fitted on this nipple 20.

[0050] The tubular member 3 is injection molded of a polyamide resin,and has a two-stage structure having a larger-diameter portion 30 and asmaller-diameter portion 31. The larger diameter portion 30 is welded atits upper end to the lower surface of the lid member 2 to form thehousing 4. The smaller-diameter portion 31 extends substantiallyvertically into the gasoline tank 1, and has such a length that itslower end opening is disposed at a liquid level of fuel when thegasoline tank 1 is full. Through holes 32 of a small diameter are formedthrough that portion of a side wall of the larger-diameter portion 30disposed at an uppermost portion of the gasoline tank 1, and theinterior of the tubular member 3 is in communication with a gas phaseportion of the gasoline tank 1 via the through holes 32.

[0051] An upper member 40 of an inverted cup-shape and a lower member 41(which is fitted in the upper member 40, and is fixed to a lower endopening thereof) are held in the larger-diameter portion 30 of thetubular member 3. The upper member 40 is abutted at its lower endagainst a step portion of the tubular member 3, and an outer peripheralsurface of this upper member is held in hermetic contact with thelarger-diameter portion 30 of the tubular member 3 through an O-ring 42,and in this manner the upper member 40 is held in the tubular member 3in fixed relation thereto. A communication opening 43, which is incommunication with the canister (not shown), is formed in an uppermostportion of the upper member 40, and communication holes 44,communicating the inside and outside of the upper member 40 with eachother, are formed through that portion of the peripheral wall of thisupper member which is disposed below the O-ring 42, and are opposed tothe through holes 32, respectively.

[0052] The lower member 41 includes an end plate 45, fitted in the loweropen end portion of the upper member 40 in fixed relation thereto, and atubular portion 46 extending upwardly from the end plate 45. A pluralityof communication holes 47 are formed through the end plate 45, that is,extend between upper and lower surfaces of this end plate, and aplurality of communication holes 48, communicating the inside andoutside of the tubular portion 46 with each other, are formed throughthe tubular portion 46.

[0053] The float valve 5 is provided within the tubular portion 46, andis placed on the upper surface of the end plate 45 through a spring 50.A plurality of vertically-extending ribs 51 are formed on an outerperipheral surface of the float valve, and the float valve can be movedupward and downward in such a manner that the ribs 51, held in contactwith an inner peripheral surface of the tubular portion 46, are guidedby this inner peripheral surface. A seal projection 52 is formed at anupper end of the float valve 5. A seal member 53 of a tubular shape,having a closed bottom, is held on an upper portion of the float valve 5so as to move upward and downward relative to this float valve, and aseal aperture 54 is formed through a central portion of the seal member53, and is opposed to the seal projection 52.

[0054] The seal member 53 is held on the float valve 5, with its bottomdisposed at the upper side. A plurality of engagement grooves 55 areformed in the outer peripheral surface of the float valve 5, and claws56, formed at an open end of the seal member 53, are engaged in theseengagement grooves, respectively. The engagement grooves 55 are largerin length than the claws 56, and the seal member 53 can slightly moveupward and downward relative to the float valve 5. When the float valve5 and the seal member 53 are moved relative to each other in a directiontoward each other, the seal projection 52 of the float valve 5 closesthe seal aperture 54 in a sealing manner.

[0055] The float valve 5 and the seal member 53 are made of a POM resin,and the apparent specific gravity of the two members is made lower thanthe specific gravity of gasoline (fuel) by their shapes and urging ofthe spring 50 so that the two members can float on liquid gasoline. Thespring 50 is held between the lower end of the float valve 5 and the endplate 45 of the housing 4, and therefore is held in such a conditionthat a urging force is stored in this spring 50. However, this urgingforce is smaller than the sum of the weights of the float valve 5 andseal member 53, and in the atmosphere and in gasoline vapor, the floatvalve 5 and the seal member 53 press the spring 50 by their own weights,so that the lower end surface of the float valve 5 is abutted againstthe end plate 45 of the lower member 41. Thus an apparent buoyancy ofthe float valve 5 and the seal member 53 is generated by a shape of thefloat valve 5 and urging of the spring 50, so that the seal member 53urgingly closes the communication opening 43 when the liquid gasolinereaches at the predetermined liquid level.

[0056] A ring-like valve seat 57 is fixed by welding to the uppersurface of the seal member 53, and a valve member 58, made of rubber, isfitted in the valve seat 57 in fixed relation thereto. When the sealmember 53 moves upward in accordance with the upward movement of thefloat valve 5, the valve member 58 is brought into sealing engagementwith a lower peripheral edge of the communication opening 43 which is incommunication with the canister.

[0057] In the fuel outflow-limiting device of this embodiment having theabove construction, in a normal condition in which the liquid level ofthe gasoline is disposed below the float valve 5, and is still, the sumof the weights of the float valve 5, seal member 53, valve seat 57,valve member 58 and spring 50 overcomes the urging force of the spring50, so that a gap is formed between the valve member 58 and the lowerperipheral edge of the communication opening 43 as shown in FIG. 2.Therefore, gas within the gasoline tank 1 passes through the throughholes 32 or the lower end opening of the tubular member 3 and throughthe communication holes 44, 47 and 48, and enters the upper member 40,and flows into the canister via the communication opening 43 and thenipple 20. As a result, the pressure within the gasoline tank 1 isprevented from increasing.

[0058] On the other hand, when the vehicle runs on a considerably-ruggedroad or when the vehicle runs along a curved road, the liquid surface ofthe gasoline is much disturbed to rise, and therefore even when theliquid level is disposed below a position where the float valve 5 isfloated in the still condition, there is a possibility that the liquidgasoline enters the interior of the housing 4 via the lower end openingof the tubular member 3 or the through holes 32 of a small diameter.However, in the device of this embodiment, the seal member 53 of thefloat valve 5 closes the communication opening 43 when the liquid levelof the liquid gasoline reaches a predetermined liquid level.Specifically, the float valve 5 and the seal member 53 are, floated bythe liquid gasoline, so that the valve member 58 closes thecommunication opening 43, and therefore the liquid gasoline is preventedfrom flowing into the canister. Even in this condition in which thevalve member 58 is held in intimate contact with the lower edge of thecommunication hole 43, when the liquid level descends, the float valve 5moves downward apart from the seal member 53, so that the seal aperture54 is opened, and as a result the pressure within the housing 4 becomesequal to the pressure within the nipple 20 communicating with thecanister, and the valve member 58 is easily separated from thecommunication hole 43. Therefore, the response is high when the liquidsurface of the gasoline is much disturbed to rise, and the dynamicsealing ability is excellent.

[0059] And besides, when the liquid level within the gasoline tank 1 isdisposed at a position A-A′, lower than the lower end opening of thetubular member 3, at the time of refueling, gas in the gas phase portionof the tank 1 flows into the canister via the lower end opening of thetubular member 3 as the liquid level rises, and therefore the refuelingoperation is continued in such a manner that the internal pressure ofthe tank 1 is not increased.

[0060] Then, when the liquid level of the gasoline reaches a positionB-B′, at which the lower end opening of the smaller-diameter portion 31of the tubular member 3 is disposed, the smaller diameter portion 31 ofthe tubular member 3 is pronged into the liquid gasoline so thatcommunication of the tubular member 3 to a gas phase located on an upperportion on the inside of the gasoline tank 1 is cut, whereby evacuationof vaporized gasoline decreases. Namely, during the refueling operation,gas in the gas phase portion of tank 1, enters the upper member 40 onlyvia the through holes 32. However, each through hole 32 is formed into asmaller diameter than the lower end opening of the tubular member 3, andtherefore offers a high ventilation resistance. Therefore, the pressurewithin the gasoline tank 1 increases, so that the filling-up of the tankcan be detected, and the operation of a refueling gun is automaticallystopped. Moreover, in this embodiment, when the level of gasoline closesthe lower edge opening of the tubular member 3, a pressure in thehousing 4 becomes lower as compared with other portions in the tank 1.Gasoline is sucked upward in the housing 4 by Venturi' effect, and thefloat valve 5 is moved upward and closes the communication opening 43.Therefore, the gasoline tank 1 is hermetically sealed and the internalpressure thereof is reliably increased. As a result, the filling-up ofthe tank can be detected precisely, and the operation of a refueling gunis automatically stopped.

[0061] For producing the fuel outflow-limiting device of thisembodiment, first, the valve seat 57 and the valve member 58 are mountedon the float valve 5, and then the float valve is inserted into thetubular portion 46 of the lower member 41, and the upper member 40 andthe lower member 41 are fitted together in fixed relation to each other.Then, this assembly is fitted into the larger-diameter portion 30 of thetubular member 3 in fixed relation thereto through the O-ring 42, andthe end of the larger-diameter portion 30 is fixed by welding to the lidmember 2. The thus formed module is inserted into the evaporationopening in the fuel tank 1, and the lid member 2 is welded to aperipheral edge portion of the evaporation opening.

[0062] Therefore, even if there exist various gasoline tanks 1 ofdifferent shapes and capacities, the device can be applied to any one ofthese tanks merely by adjusting the length of the tubular member 3, andthe other parts can be used as common parts, and therefore the cost canbe greatly reduced. And besides, the device can be fixed by welding to aportion of the gasoline tank 1 having a very small area, and thereforethe mounting space is small, and the degree of freedom with respect tothe mounting position is high.

[0063] (Second Embodiment)

[0064]FIG. 3 shows a second embodiment of a fuel outflow-limiting deviceof the invention. In this device, a housing 4 comprises an upper member40 and a lower member 41. A tubular member 3 includes a tubular portion33, and a flange portion 34 formed at one end of the tubular portion 33,and the flange portion 34 is welded to ends of the upper and lowermembers 40 and 41. Through holes 32 of a small diameter are formedthrough a peripheral wall of the upper member 40. The other constructionis similar to that of the first embodiment.

[0065] In this device, also, similar operational effects as in the firstembodiment can be achieved.

[0066] In the above embodiments, although the device is fixed to thegasoline tank 1 by welding the lid member 2 to the gasoline tank 1, alid member 2 maybe fastened through a packing 21 to the gasoline tank 1by bolts 6 or the like, as shown in FIG. 4. As shown in FIG. 5, thedevice can be fixedly mounted within the gasoline tank 1 in a suspendedmanner by the use of mounting metal members 7. In this case, the lengthof a tubular member 3 is smaller as compared with the second embodiment.

[0067] (Third Embodiment)

[0068]FIG. 6 shows a third embodiment of a fuel outflow-limiting deviceof the invention. In this device, a relief mechanism 60 is provided onthe outer side of the housing 4 within the cover member 2. The reliefmechanism 60 is constituted by a bleeding passage 61 connecting theinside and the outside of the tank 1 and a ball valve 62 urged by aspring 63 and configured to open and close the bleeding passage 61 inaccordance with the internal pressure of the tank 1. The ball valve 62is usually urged in a direction toward the inside of the tank 1 so as toclose the opening of the bleeding passage 61 on the side of the tank 1.However, as the internal pressure of the tank 1 is increased beyond apredetermined pressure, the ball valve 62 is pressurized and displacedagainst the urging of the spring 63 in a direction allowing the bleedingpassage 61 to open. The relief mechanism 60 connects the inside and theoutside of the gasoline tank 1. Thus the relief mechanism 60 is openedso as to bleed the gas in the gasoline tank 1 when an internal pressureof the tank 1 rises beyond the predetermined pressure. By such themechanism, it is prevented that the internal pressure of the tankbecomes abnormally higher.

[0069] (Fourth Embodiment)

[0070]FIG. 7 shows a fourth embodiment of a fuel outflow-limiting deviceof the invention.

[0071] The float valve 5 is provided within the larger diameter portion30. Instead of the ribs 51 in FIG. 2, a plurality of ribs 59 areextended vertically and radially from an outer peripheral surface of thefloat valve 5. The outer ends of the ribs 59 abut with the inner surfaceof the larger diameter portion 30 so that movement of the float valve 5in the larger diameter portion 30 is guided upward and downward by thelarger diameter portion 30. Basically number of the fins is notspecifically limited by eight fins are radially provided in thisembodiment. By such the structure, it is not necessary to form tubularportion for guiding the float valve such as the tubular portion 46 ofthe first embodiment as shown in FIG. 2. Therefore, the structure of thedevice can be simplified. Incidentally, in this embodiment, although thelarger diameter portion 30 and the smaller diameter portion 31 areformed in two-piece, these members may be integrally formed.

[0072] Further, in the third and fourth embodiments, welded portions 70among the cover member 2, the larger-diameter portion 30 and the uppermember 40 in FIGS. 6 and 7 are welded by laser welding. By such thestructure, it is not necessary to provide O-ring between thelarger-diameter portion 30 and the upper diameter portion 40. Here, thehousing 4 is formed with the upper portion 40 and the larger diameterportion 30. Therefore, not only similar operational effects as in thefirst and second embodiments can be achieved, but also the number ofcomponents can be reduced more in these embodiments.

[0073] With respect to the connecting structures by which the lid member2, the upper member 40, the lower member 41 and the tubular member 3 arejoined together, any suitable engagement means, such as welding andclaw-engagement means, other than those of the above embodiments can beused.

[0074] Namely, in the fuel outflow-limiting device of the presentinvention, the full-tank detection and the cutoff operation can beeffected by the single device of the unitary construction, and besidesonly one opening need to be formed in the fuel tank, and therefore thisdevice is very effective from the viewpoint of the mounting space.Furthermore, the device can be applied to various fuel tanks merely byadjusting the length of the tubular member, and therefore the time andlabor are much reduced, and the cost can be greatly reduced.

What is claimed is:
 1. An outflow-limiting device of a fuel tank,comprising: a housing, which is fixed to an upper wall of the fuel tank,and has a communication opening in communication with a canister; afloat valve which is received within the housing, and floats on a liquidfuel, and moves upward and downward in accordance with the upward anddownward movement of a liquid level of a fuel so as to close and openthe communication opening; a tubular member which communicates with thehousing, and extends downwardly from the housing into an interior of thefuel tank, and at a lower end of which an lower end opening is formed;and a through hole of a smaller diameter than the lower end openingwhich is disposed near an inner surface of the upper wall of the fueltank, and communicates an inside and outside of the housing with eachother; wherein when the liquid level of the fuel in the fuel tankreaches the lower end opening of the tubular member, a pressure withinthe fuel tank increases, so that the tubular member detects a filling-upof the fuel tank, and when liquid level of the fuel rises beyond apredetermined normal level, the float valve closes the communicationopening.
 2. An outflow-limiting device of a fuel tank according to claim1, wherein the tubular member is separate from the housing, and ishermetically fixed to the housing.
 3. An outflow-limiting device of afuel tank according to claim 1, wherein an upwardly-open tubular portionis formed within the housing, and is disposed around an outer peripheryof the float valve.
 4. An outflow-limiting device of a fuel tank,comprising: a housing in which a float valve chamber is formed and whichis provided with a communication opening to an outside of the fuel tank;a tubular member communicating and extending downward from the housingin a direction of liquid level of a fuel and having a lower end openingat a lower end thereof; a through hole having a smaller diameter thanthe lower end opening, formed on a position upper than the lower endopening so as to communicate with the tubular member or the float valvechamber; a float valve provided in the float valve chamber; and a sealmember attached to the floating valve for closing the communicationopening; wherein the tubular member is pronged into the fuel when theliquid level of the fuel reaches a first liquid level of the fuel sothat communication of the tubular member to a gas phase located on anupper portion on the inside of the fuel tank is cut, whereby evacuationof vaporized fuel decreases.
 5. An outflow-limiting device according toclaim 4, wherein the seal member of the float valve closes thecommunication opening when the liquid level of the fuel reaches a secondliquid level.
 6. An outflow-limiting device according to claim 5,wherein the float valve is urged upward in the liquid level directionwith a spring.
 7. An outflow-limiting device according to claim 6,wherein an apparent buoyancy of the float valve and the seal member isgenerated by a shape of the float valve and urging of the spring, sothat the seal member urgingly closes the communication opening when theliquid fuel reaches at the second liquid level.
 8. An outflow-limitingdevice according to claim 4, wherein the float valve includes a sealaperture connected to the communication opening and having a smallerdiameter than the communication opening and a seal projection configuredto be openable and closable of the seal aperture.
 9. An outflow-limitingdevice according to claim 4, wherein a plurality of fins radiallyextended from an outer peripheral surface of the float valve, and outerends of the fins abut with an inner surface of the housing so thatmovement of the float valve is guided.
 10. An outflow-limiting deviceaccording to claim 4, further comprising a relief mechanism connectingthe inside and the outside of the fuel tank wherein the relief mechanismis opened so as to bleed the gas in the fuel tank when an internalpressure of the fuel tank rises beyond a predetermined pressure.
 11. Anoutflow-limiting device according to claim 4, wherein a valve member ofthe seal member is constituted by a rubber material.
 12. Anoutflow-limiting device according to claim 4, wherein the float valve isconstituted by a POM resin.
 13. An outflow-limiting device according toclaim 4, wherein a length of the tubular member is determined so as tocorrespond to the first liquid level.
 14. An outflow-limiting deviceaccording to claim 4, wherein the fuel tank is served in an automobileand the communication opening is communicated with a canister.